The tag [mapreduce] doesn't have a user guidance. Currently it has questions that cover both the technique of "Map-Reduce" from concurrent algorithms and "map reduction" from theory of computability.
Currently it has only 11 questions, most of them about concurrent programming. So I suggest:
- remove the tag; or
- write a user guide specifying the tag is about concurrent programming, and remove the tag from questions about computer theory.
Either fixes would be very easy. However I would prefer option #2. This tag has been seldom used, but this might be because it lacks user guidance.